Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$85.71	9.192%	$93.5885	$93.59	$93.60	$93.60
Purchase #2	$155.31	11.735%	$173.5356	$173.54	$173.55	$173.50
Purchase #3	$122.42	6.793%	$130.736	$130.74	$130.75	$130.70
Purchase #4	$98.36	3.820%	$102.1174	$102.12	$102.10	$102.10
Purchase #5	$79.81	12.707%	$89.9515	$89.95	$89.95	$90.00
Purchase #6	$178.92	6.534%	$190.6106	$190.61	$190.60	$190.60
Purchase #7	$105.31	7.862%	$113.5895	$113.59	$113.60	$113.60
7 purchase totals =	$825.84		$894.1291	$894.14	$894.15	$894.10